On Tue, 2022-02-08 at 13:10 +0000, Matthew Wilcox wrote: > On Tue, Feb 08, 2022 at 12:01:22PM +0100, Julian Andres Klode wrote: > > It's worth pointing out that in Ubuntu, the generated MOK key > > is for module signing only (extended key usage > > 1.3.6.1.4.1.2312.16.1.2), kernels signed with it will NOT be > > bootable. > > Why should these be separate keys? There's no meaningful security > boundary between a kernel module and the ernel itself; a kernel > modulecan, for example, write to CR3, and that's game over for > any pretence at separation. It's standard practice for any automated build private key to be destroyed immediately to preserve security. Thus the modules get signed with a per kernel ephemeral build key but the MoK key is a long term key with a special signing infrastructure, usually burned into the distro version of shim. The kernel signing key usually has to be long term because you want shim to boot multiple kernels otherwise upgrading becomes a nightmare. James
